Control mechanism for sawmill carriage steam feeds



Jan. 13, 1942. f M. KAHR 2,270,059

CONTROL MECHANISM FOR SAWMILL CARRIAGE STEAM FEEDS Filed Nov. 7, 193B 2Sheets-Sheet 1 "aQL Y INVENTOR. v Ward/n ffahr' ATTORNEY.

M. KAHR 2,270,059

CONTROL MECHANISM FOR SAWMILL CARRIAGE STEAM FEEDS Jan. 13, 1942.

Filed Nov. '7, 1938 2 Sheets-Sheet 2 WW QQ m ZLEJW ww R Iiiii INVENTOR.BY mam/n K357" b ATTORNEY.

Patented Jan. 13, 1942 CONTROL MECHANISM FOR SAWMI LL CARRIAGE STEAMFEEDS Martin Kahr, Milwaukee, Wis., assignor to The Filer & Stowell(10., Milwaukee, Wis., a corporation of Wisconsin Application November7, 1938, Serial No. 239,204

3 Claims. (01. 121-41) This invention relates to an improvement incontrol mechanism for saw mill carriage steam feeds.

Saw mill carriages are commonly reciprocated by means of a reciprocatingsteam engine which usually has a fixed cylinder and a reciprocatingpiston, the latter being connected to the carriage. The distribution ofthe steam supply to the opposite ends of the cylinder is controlled bymeans of distributing valves which are necessarily rather large andheavy and this, together with the necessity for very rapid operation ofthe carriage, has led to the use of a servo-motor for operating thevalve. The action. of the servomotor is controlled by means of the pilotvalve, regulated in its action from a control lever which may beconveniently manipulated by the sawyer. The nature of the organizationand particularly the inertia of the various parts renders it difiicultfor the sawyer to readily and easily exert an exact control over theoperation of the servo-motor. The piston of the servo-motor tends toovertravel and impair the intended operation of the pilot valve by whichit is controlled.

The principal object of the present invention is to so interrelate andinterconnect the piston of the servo-motor and its pilot valve as todampen the action of these parts and overcome the disturbing actions ofinertia with the result that the sawyer can very conveniently exercisejust the control he desires over the action of the servomotor and theconsequent actuation of the saw mill carriage.

Another object of the invention is to provide a control device of thischaracter which is extremely simple and compact in its construction,reliable, smooth and eflicient in its operation, readily and easilycontrollable, and easy and comparatively inexpensive to manufacture andinstall. I

Other objects and advantages reside in certain novel features of theconstruction, arrangement and combination of parts which will behereinafter more fully described and particularly pointed out in theappended claims, reference being had to the accompanying drawingsforming a part of this specification, and in which:

Figure 1 is a diagrammatic view in elevation illustrating the generallayout of a steam feed for saw mill carriages equipped with a steamvalve controller embodying the present invention;

Figure 2 is a similar view in top plan of the structure shown in Figure1;

tion looking toward the left hand end of-Figure 2, parts being shown insection for the sake of example and illustration; I

Figure 4 is a view in vertical section taken on line 44 of Figure 2,parts being shown in elevation for the sake of illustration;

Figure 5 is a view partly in section and partly in elevation showing thedampening device of the present invention on an enlarged scale; and

Figure 6 is a view in vertical cross section taken on line 66 of Figure5.

Referring to the drawings, the numeral Ill designates the cylinder of asaw mill carriage steam feed which is of conventional construction andfixed in place in the usual manner. The piston reciprocable in thecylinder is not shown but it has a piston rod II which is connected inthe usual way to the saw mill carriage.

Steam is supplied from a boiler (not shown) through a pipe l2 which hasbranches l3 and it connected to the inlet sides of steam feed valves I5and I6 which control the passage of the steam through the inlet pipes I1and I8 communicating with the opposite ends of the cylinder H3. The feedvalves l5 and I6 are opened and closed by the usual valve gear,designated generally at 20, and have a main operating rod 2| suitablycoupled as at 22 to the piston rod 23 of a servo-motor designatedgenerally at 24.

The servo-motor 24 is of conventional construction' and has a fixedcylinder 25 suitably supported and a piston 26 reciprocable in thecylinder 25. The piston rod 23 is threadedly connected as at 21 to oneend of the piston, the threaded connection being maintained by means ofa lock nut 28. Steam is supplied to the cylinder 25 from the boiler to asteam pipe 29 which has branches 30 and 3| in open and constantcommunication with the opposite ends of the cylinder.

The piston 26 is formed with spaced heads 32 and 33 having piston rings34 to establish a fluid tight sliding relation between the piston headsand the wall of the cylinder. The body portion of the piston in betweenits spaced heads is of less diameter than the cylinder to define anexhaust space 36 with which an exhaust pipe 31 is in constantcommunication. An axial opening or bore 38 extends through the heads andbody of the piston from one end thereof to the other although the endsof this bore are eiiectively closed on by means of the piston rod 23 anda companion piston rod 23' and associated structure. At the center ofthe body portion of the Figure 3 is a fragmentary view in endelevapiston 26 a chamber 40 is provided and communicates with theexhaust space 36 at all times through a port 4|. On the opposite sidesof the chamber 40 annular grooves 42 and 43 are provided and thesegrooves respectively communicate with the inner ends of steam passages44 and 45. The passages 44 and 45 lead from their respective grooves cutthrough the ends of the piston and consequently are in communication atall times with the steam pressure always maintained at the opposite endsof the cylinder. .A piston type pilot valve designated generally at 46is provided and has spaced piston heads 41 and 48 fitted in the axialopening or bore 38 of the.

piston of the servo-motor and respectively cooperable with the annulargrooves 42 and 43 either to plug these grooves or else to selectivelyuncover them and allow steam to flow therethrough to the exhaust andconsequently reduce the pressure on one side or the other of the pistonand cause it to be moved toward one end or the other of the cylinder.Such motions of the piston moves the piston rod 23 in one direction orthe other and consequently serves to open or close the steam feed valvedepending, of course, on the direction of the motion. The companionpiston rod 23 is in the form of a pipe or tube and works through astufiing box 50 provided on one of the end heads of the cylinder 25. Thepilot valve 46 has an elongated valve stem 5| which extends back throughand beyond the-hollow piston rod 23. A cross head 52 has its hubthreadedly connected with the outer end of the piston rod 23 and it isheld in adjusted position thereon by means of a lock nut 53. The outerend of. the piston rod 23' is provided with a packing gland 54 throughwhich the stem of the pilot valve extends. Just beyond the packing gland54 a second cross head, designated at 55, is provided and has its hubthreadedly interconnected with the threaded outer end 5| of the valvestem 5|. A look nut 56 maintains the adjustment of the cross head 55. Aclevis 51 is interconnected with the outer end of the valve stem 5| justbeyond the cross head and is connected through a system of links andlevers designated generally at 58 with the manually operable controllever 59. Rods 60, preferably two in number, extend from the cross head52 through openings 6| in the cross head 55 and beyond the same. Nuts 63secure one end of each of the rods to the cross head 52. Theintermediate portions of the rods are slidably interfitted with theopening 6| in the cross head 55. Compression coil springs 64 encirclethe rods 65 between the cross heads 52 and 55 and abut these cross headsat theiropposite ends. Springs 65 encircle the portions of the rodsprojecting beyond the cross head 55 and their inner ends engage thiscross head while their outer ends engage one of a pair of nuts 66threaded on the outer ends of the rods 60. The springs are undercompression which may, of course, be varied by suitably adjusting thecross heads relative to each other and the nuts 66.

In practice, the valve controllers embodying the present invention aretested before shipment and the springs 64 and 65 are so adjusted thatthe pilot valve 45 is centrally located in the piston of the servo-motorand the control lever moves with equal ease in either direction. Whenthis is accomplished, the operation is then very smooth and the controllever 59 can then be moved very easily. This also has the effect, withthe springs appropriately tightened, to dampen any vibration that mightotherwise be set up by the pilot valve 46 and the piston 26 of theservo-motor.

When making the adjustment described the linkage to the right of part 51is disconnected and the lock nut 56 is loosened. The whole assemblyshown in Figure 5 can then be rotated on the piston rod 23'. Theconsequent shifting of the yoke 52 changes the tension of the springs64. The tension of the springs 65 is adjusted by adjusting the nuts 66.Of course, after the appropriate adjustments are made the several locknuts are tightened and the operating or control linkage reconnected.With a valve controller of this character, when the operating or controllever 59 is moved to shift the pilot valve 46 with respect to the piston26 and thereby reduce the pressure on one side or the other of thepiston and cause it to move correspondingly, it moves without the piston26 tending to overtravel since the motion is dampened by the action ofthe springs 64 and 65 or interconnected in the manner described betweenthe piston rod of the servomotor piston and the valve stem of the pilotvalve.

While I have shown and described one construction in which the inventionmay be advantageously embodied, it is to be understood that theconstruction shown has been selected merely for the purpose ofillustration or example and that various changes in the size, shape andarrangement of the parts may be made without departing from the spiritof the invention or the scope of the subjoined claims.

The invention claimed is:

1. A control mechanism comprising a servomotor having a piston rod, apilot valve for said servo-motor, said valve having an operating stemshiftable axially of said rod, and means interconnecting said stem androd and comprising spaced cross heads connected to said stem and to saidrod, guide rods secured to one of said cross heads, the other of saidcross heads having openings through which the guide rods slidablyextend, the guide rods projecting beyond said lastnamed cross head,compression coil springs encircling the guide rods and abutting thecross heads at the opposite ends, and a second set of coil springsencircling the projecting portions of the guide rods and abutting one ofthe cross heads at their inner ends, and adjustable abutments for theouter ends of said springs mounted on the outer end portions of saidguide rods.

2. A control mechanism for saw mill carriage steam feeds comprising aservo-motor having a cylinder, a piston in the cylinder having a pistonrod extending beyond one end thereof and adapted for connection with thevalve gear of the steam feed, a hollow piston rod extending through atone end of the cylinder, a pilot valve associated with. the piston ofthe servo-motor and shiftable axially thereof to control the motions ofsaid piston, a stem connected to the pilot valve and extending throughand beyond the hol- 10W piston rod, a control lever operativelyinterconnected with said stem, and means interconnecting the valve stemand the hollow piston rod and comprising spaced cross heads connected tosaid valve stem and to said hollow piston rod, rods secured to one ofsaid cross heads, the other of said cross heads having openings throughwhich the rods slidably extend, the rodsprojecting beyond said lastnamed cross head, compression coil springs encircling the rods andabutting the cross heads at the opposite ends and 3/5861 ond set of coilsprings encircling the projecting portions of the rods and abutting oneof the cross heads at their inner ends, and adjustable abutments for theouter ends of said springs mounted on the outer end portions of saidrods.

3. A control mechanism for saw mill carriage steam feeds comprising aservo-motor having a cylinder, a piston in the cylinder having a pistonrod extending beyond one end thereof and adapted for connection with thevalve gear of the steam feed, a hollow piston rod extending through atone end of the cylinder, a pilot valve associated with the piston of theservo-motor and shiftable axially thereof to control the motions of saidpiston, a stem connected to the pilot valve and extending through andbeyond the hollow piston rod, a control lever operatively interconnectedwith said stem, and means interconnecting the valve stem and the hollowpiston rod and comprising spaced cross heads connected to said valvestem and to said hollow piston rod, rods secured to one of said crossheads, the other of said cross heads having openings through which therods slidably extend, the rods projecting beyond said last named crosshead, compression coil springs encircling the rods and abutting thecross heads at the opposite ends, and a second set of coil springsencircling the projecting portions of the rods and abutting one of thecross heads at their inner ends, and adjustable abutments for the outerends of said springs mounted on the outer end portions of said rods, thecross head connected to the hollow piston rod being adjustabletherealong to vary the tension of the 15 springs engaged by it.

MARTIN KAHR.

